This invention relates to mechanical power presses for stamping sheet material and the like and more particularly to the type of power press known in the art as a mechanical press wherein the frame of the press has a base portion for receiving sheet metal stamping or forming dies and the crown of the press has eccentric or crankshaft means for driving a vertically reciprocal slide toward and away from the bed of the press to effect pressing strokes. The slide is supported and guided for such reciprocation by the frame of the press.
Mechanical presses of this type are well known and it is likewise known to provide in conjunction with the vertically reciprocable slide of the press hydraulic overload features which are arranged to shut the press down when predetermined pressing forces are exceeded. This has been accomplished in the prior art by interposing hydraulic means in the slide of the press in such a way that when a given determined hydraulic pressure force is exceeded, the hydraulic protective valves open and operate means for shutting the press down until the malfunction causing the excessive pressing force is corrected. A typical hydraulic means for providing such an overload arrangement is shown in Spanke U.S. Pat. No. 4,166,415 although this general hydraulic overload system has been known and used for many years.
It is also known to provide hydraulic means operable to raise the slide of the press independently of the mechanical drive thereof in order to expose the die on the bed of the press for adjustment or other servicing.
It is known in the prior art of mechanical presses to provide hydraulic means in conjunction with the crown of the press for raising the same to raise the slide of the press and thus expose the die on the bed of the press for purposes similar to herein contemplated. However, use of the hydraulic means in conjunction with the crown of the press is limited to this stated purpose. Examples of die inspection arrangements of this type are shown in Wrona U.S. Pat. No. 3,400,625 and Wrona U.S. Pat. No. 3,662,640. The present invention contemplates self-contained means means acting between the mechanical connection or pitman of the press and the slide of the press in effecting all three of the above stated purposes.